Vitamin D

Vitamin D3, or cholecalciferol, is not a vitamin in the proper sense. It is a hormone derived from the stress hormone, cortisol.

Origin

Vitamin D is the result of the molecular transformation of cortisol under the skin, under the influence of sunlight, particularly UVB (ultraviolet light with a wavelength of 300 nm).

Usage

The main function of vitamin D3 is to maintain and regulate the metabolism of calcium in the body. Consequently, it is crucial for the development and preservation of a strong and healthy skeleton. Vitamin D insufficiency increases the risk of osteoporosis, but it is also associated with an increased risk of high blood pressure. _{1, 2, 3} As a result, there is an increasing awareness of the importance of sufficient levels of vitamin D3 as a condition for optimal health. Vitamin D is transformed into its biologically active form in the skin through the photochemical conversion of provitamin D and additional transformation in the liver and the kidneys. However, the UVB rays required to achieve the transformation are not present all year round in regions with a latitude of under 35 °.₄ For those living north of this latitude, it is essential to ensure a daily intake of vitamin D. Very few dietary sources naturally contain vitamin D. This often leads to low plasma levels. The general population does not respect the minimum requirements for vitamin D. _{5, 6, 7} This is particularly true for people who spend most of their time indoors, or who have dark skin. Oily fish contains the highest levels of the vitamin. Vitamin D2 is produced by mushrooms. It has also been discovered that vitamin D has a significant modulating effect on the adaptive and innate immune system, and on deficiencies associated with upper respiratory tract infections such as colds, bronchitis and the flu _9,10. Vitamin D3 plays such an important role in resistance because it transforms the immune cells to produce substances that have a powerful effect against a range of bacteria and viruses. _11,12 Recent research demonstrates that vitamin D3, in addition to the winter diet, is the safest way of reducing the number of cases of flu and infections in children, and in particular in children with a vitamin D3 deficiency._{13, 14, 15}

Bibliographical references

₁Overview of general physiologic features and functions of vitamin D.
DeLuca HF
Am J Clin Nutr. 2004 Dec; 80(6 Suppl):1689S-96S.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/15585789

₂ Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease.
Holick MF
Am J Clin Nutr. 2004 Dec; 80(6 Suppl):1678S-88S.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/15585788

₃ 25-Hydroxyvitamin D deficiency is independently associated with cardiovascular disease in the Third National Health and Nutrition Examination Survey.
Kendrick J, Targher G, Smits G, Chonchol M
Atherosclerosis. 2009 Jul; 205(1):255-60.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/19091317

₄ Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.
Webb AR, Kline L, Holick MF.
J Clin Endocrinol Metab. 1988 Aug;67(2):373-8.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/2839537

₅ Global vitamin D status and determinants of hypovitaminosis D.
Mithal A, Wahl DA, Bonjour JP, Burckhardt P, Dawson-Hughes B, Eisman JA, El-Hajj Fuleihan G, Josse RG, Lips P, Morales-Torres J; IOF Committee of Scientific Advisors (CSA) Nutrition Working Group.
Osteoporos Int. 2009 Nov;20(11):1807-20.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/19543765

₆ Vitamin D deficiency is common among adults in Wallonia (Belgium, 51°30' North): findings from the Nutrition, Environment and Cardio-Vascular Health study.
Hoge A, Donneau AF, Streel S, Kolh P, Chapelle JP, Albert A, Cavalier E, Guillaume M
Nutr Res. 2015 Aug;35(8):716-25.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/26149190

₇ Vitamin D: An overview of vitamin D status and intake in Europe
A Spiro, J L Buttriss
Nutr Bull. 2014 Dec; 39(4): 322–350.
PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288313/

₈ The Active Metabolite of Vitamin D3 as a Potential Immunomodulator
I. Szymczak, R. Pawliczak
Scand J Immunol. 2016 Feb;83(2):83-91.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/26678915

₉ Epidemic influenza and vitamin D.
Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E.
Epidemiol Infect. 2006 Dec;134(6):1129-40.
PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870528/

_1° Serum Vitamin D Levels in Children with Recurrent Respiratory Infections and Chronic Cough
Özdemir B, Köksal BT, Karakaş NM, Tekindal MA, Özbek ÖY
Indian J Pediatr. 2016 Aug; 83(8):777-82.
ResearchGate: https://www.researchgate.net/publication/292209876_Serum_Vitamin_D_Levels_in_Children_with_Recurrent_Respiratory_Infections_and_Chronic_Cough

₁ Antiviral activity and increased host defense against influenza infection elicited by the human cathelicidin LL-37.
Barlow PG, Svoboda P, Mackellar A, Nash AA, York IA, Pohl J, Davidson DJ, Donis RO
PLoS One. 2011; 6(10):e25333.
ResearchGate: https://www.researchgate.net/publication/51749566_Antiviral_Activity_and_Increased_Host_Defense_against_Influenza_Infection_Elicited_by_the_Human_Cathelicidin_LL-37

₁₂ Direct inactivation of viruses by human granulocyte defensins.
Daher KA, Selsted ME, Lehrer RI.
J Virol. 1986 Dec;60(3):1068-74.
PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC253347/

₁₃ Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.
Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H
Am J Clin Nutr. 2010 May; 91(5):1255-60.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/20219962

₄ Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.
Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H
Am J Clin Nutr. 2010 May; 91(5):1255-60.
PubMed: https://www.ncbi.nlm.nih.gov/pubmed/20219962

₅ Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.
Martineau AR et al.
BMJ. 2017; 356: i6583.
The BMJ: https://www.bmj.com/content/356/bmj.i6583

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